Systems and methods for adjusting electrical therapy based on impedance changes

Abstract

System and methods for adjusting electrical therapy based on impedance changes are disclosed herein. A method in accordance with a particular embodiment includes applying a therapeutic electrical signal to a patient via an implanted portion of a patient stimulation system that includes a signal delivery device in electrical communication with a target neural population of the patient. The electrical signal is delivered in accordance with a signal delivery parameter having a first value. Using the implanted portion of the patient stimulation system, a change in an impedance of an electrical circuit that includes the signal delivery device is detected. Based at least in part on the detected impedance change, the method can further include automatically adjusting the value of the signal delivery parameter from the first value to a second value different from the first, without human intervention.

We claim: 
     
       1. A patient therapy system, comprising:
 an implantable pulse generator having a computer-readable medium, wherein the pulse generator is electrically coupleable to a signal delivery device to form an electrical circuit that includes an electrical contact carried by the signal delivery device, and wherein the computer-readable medium contains instructions that, when executed,
 (a) determine an impedance of the electrical circuit, and 
 (b) in response to a decrease in the impedance, automatically adjust a therapy signal parameter in accordance with which an electrical signal is delivered via the electrical contact. 
 
 
     
     
       2. The patient therapy system of  claim 1  wherein the computer-readable medium further contains instructions that, when executed, automatically decrease a strength of the electrical signal in response to the decrease in impedance. 
     
     
       3. The patient therapy system of  claim 2  wherein the electrical contact is a first electrical contact, the signal delivery device further having a second electrical contact, and wherein the instructions, when executed, and in response to the decrease in the impedance, initiate delivery of a second electrical signal via the second electrical contact. 
     
     
       4. The patient therapy system of  claim 1  wherein the computer-readable medium further contains instructions that, when executed, automatically decrease a voltage of the electrical signal in response to the decrease in impedance. 
     
     
       5. The patient therapy system of  claim 1  wherein the computer-readable medium further contains instructions that, when executed, automatically decrease a current of the electrical signal in response to the decrease in impedance. 
     
     
       6. The patient therapy system of  claim 1  wherein the computer-readable medium further contains instructions that, when executed, automatically stop delivery of the electrical signal via the electrical contact in response to the decrease in impedance. 
     
     
       7. The patient therapy system of  claim 1  wherein the computer-readable medium further contains instructions that, when executed, determine an impedance trend based on identified changes in the impedance. 
     
     
       8. A patient therapy system, comprising:
 an implantable pulse generator having a computer-readable medium, wherein the pulse generator is electrically coupleable to a signal delivery device to form an electrical circuit that includes an electrical contact carried by the signal delivery device, and wherein the computer-readable medium contains instructions that, when executed,
 (a) determine an impedance of the electrical circuit, and 
 (b) in response to a decrease in the impedance, automatically adjust a therapy signal parameter in accordance with which a first electrical signal is delivered via the electrical contact, wherein determining the impedance of the electrical circuit includes determining the impedance via a second electrical signal, wherein the first electrical signal is a therapeutic electrical signal, and wherein the second electrical signal is a non-therapeutic electrical signal. 
 
 
     
     
       9. A patient therapy system, comprising:
 an implantable pulse generator having a computer-readable medium, wherein the pulse generator is electrically coupleable to a signal delivery device to form a first electrical circuit that includes a first electrical contact carried by the signal delivery device and a second electrical circuit that includes a second electrical contact carried by the signal delivery device, and wherein the computer-readable medium contains instructions that, when executed,
 (a) determine an impedance of the first electrical circuit, 
 (b) in response to a first increase in the impedance to a value less than a threshold value of impedance, automatically adjust a compliance value in accordance with which a first electrical signal is delivered via the first contact, wherein the threshold value of impedance is indicative of an open circuit, and wherein the compliance value corresponds to a value of impedance that is less than the threshold value of impedance, and 
 (c) in response to a second increase in the impedance to a value greater than the threshold value of impedance, initiate delivery of a second electrical signal via the second contact. 
 
 
     
     
       10. The patient therapy system of  claim 9  wherein the computer-readable medium further contains instructions that, when executed, measure the impedance of the first electrical circuit via a third electrical signal, wherein the first and second electrical signals are therapeutic, and wherein the third electrical signal is non-therapeutic. 
     
     
       11. The patient therapy system of  claim 10  wherein the computer-readable medium further contains instructions that, when executed, and in response to the second increase in impedance, monitor the first electrical circuit for a decrease in impedance. 
     
     
       12. The patient therapy system of  claim 11  wherein the computer-readable medium further contains instructions that, when executed, and in response to a decrease in the impedance below the threshold value, initiate delivery of the first electrical signal via the first electrical circuit. 
     
     
       13. The patient therapy system of  claim 9  wherein the implantable pulse generator further includes a constant current source, and wherein the constant current source adjusts a voltage of the first electrical signal to maintain a current of the first electrical signal. 
     
     
       14. The patient therapy system of  claim 9  wherein the computer-readable medium further contains instructions that, when executed, and in response to the second increase in impedance, provide a notification of an open circuit. 
     
     
       15. A patient therapy system, comprising:
 an implantable pulse generator electrically coupleable to a signal delivery device having an electrical contact positionable to be in electrical communication with a target neural population of a patient when implanted; 
 an impedance detector disposed within the implantable pulse generator, the impedance detector operatively coupleable to an electrical circuit that includes the electrical contact to detect an impedance of the electrical circuit; and 
 a processor disposed within the implantable pulse generator, the processor having a computer-readable medium programmed with instructions that, when executed,
 (a) receive an indication of an impedance change from the impedance detector, and 
 (b) based at least in part on the detected impedance change and without human intervention, automatically adjust a value of a signal delivery parameter in accordance with which the implantable pulse generator delivers an electrical signal to the electrical contact, wherein automatically adjusting a value of a signal delivery parameter includes automatically adjusting a compliance value in accordance with which the electrical signal is delivered, and wherein the compliance value corresponds to a value of impedance that is less than a threshold value of impedance. 
 
 
     
     
       16. The patient therapy system of  claim 15  wherein the processor is programmed with instructions that, when executed, provide a notification that the value of the signal delivery parameter has been adjusted. 
     
     
       17. The patient therapy system of  claim 15  wherein the implantable pulse generator includes a constant current source having a compliance voltage level with a first value, and wherein the processor further includes computer-readable instructions that, when executed,
 automatically increase the compliance voltage level from the first value to a second value higher than the first value, and 
 automatically increase a strength of the signal beyond a strength available with the first value. 
 
     
     
       18. The patient therapy system of  claim 15  wherein the processor is programmed with instructions that, when executed, identify changes in impedance as a function of time. 
     
     
       19. The patient therapy system of  claim 18  wherein the processor is programmed with instructions that, when executed, predict a future value of the impedance. 
     
     
       20. The patient therapy system of  claim 15  wherein the signal delivery device includes a plurality of additional electrical contacts, and wherein the processor is programmed with instructions that, when executed, automatically changes the electrical contacts to which the electrical signal is applied, in response to the indication of an impedance change.